1. Field of the Invention
This invention relates generally to controlling a vehicle transmission pump.
2. Description of the Prior Art
Engine start-stop technology comes with significant benefits to automotive technologies. It is generally, more fuel economic to be able to routinely turn the engine off in-part or in-full when driving. Other powertrain systems respond to the engine status. For example transmissions linked to the engine have operating schemes that are governed according to whether the engine is on or off—e.g., in hybrid vehicles the electrically variable transmissions can disengage the clutch and rely on motor power. In most transmissions fluid pressure is maintained within a certain range while the transmission is operating. When an engine is first starting, however, the transmission subsystems can require time to work up to performance at a desired level, e.g., a transmission fluid pump can require priming due to air entrapment from oil sloshing. If the transmission pump is used without being primed re-starts can be relatively harsh on transmission components. It is therefore, desirable to have control logic for transmission pump priming in vehicles that employ start-stop technology for the engine.
One U.S. Pat. No. 7,465,250 titled “On-Board Hybrid Transmission Auxiliary-Pump Priming Control System” discusses priming a transmission pump when the engine is off based on the pressure in the transmission. Pressure sensors are added or linked to the pump controller in order to effectuate pump priming. The additional sensors can be expensive to add or complicated to direct to the pump controller. Moreover, it would be beneficial to have pump control logic that is tailored for engine start-stop events and not just programmed to run when the vehicle engine is off.
Therefore, it is ultimately desirable to have a method of controlling a start-stop vehicle transmission pump. It is further desirable to have said method be capable of actuation without the use of pressure sensing devices.